Tunnel vision in a leader can produce the intense focus that solves challenging problems. But tunnel vision that misses the big picture can also be futile.

This is the best frame with which to see President Donald Trump’s growing threat to force a partial government shutdown at midnight Friday by refusing to sign a spending resolution unless Congress agrees to provide $5 billion for Trump’s main obsession: building that border wall. This may resonate with the 40 percent or so of Americans who approve of Trump. But he doesn’t have the support of Republican lawmakers, who realize that a shutdown will be blamed on them as well as the president.

Senate Majority Leader Mitch McConnell, R-Kentucky, and House Speaker Paul Ryan, R-Wisconsin, indicated in October they were ready — “committed” in McConnell’s words — for what Ryan called a “big fight” over the border wall. But since Republicans lost 40 seats in the House last month, they’ve shown no sign of craving such a battle. Still, Trump may see a shutdown as a way to take the focus off his legal woes and a plunging stock market.

Funding is set for Social Security, Medicare and Medicaid and most of the government because of entitlement spending rules and already-approved legislation. But a partial shutdown would affect the Departments of Homeland Security, Treasury and Commerce as well as some lower-profile agencies.

Since Trump has no hope of winning this fight, what he plans to do is more akin to a tantrum than political hardball. If chaos results at airports and in financial markets, he should look in the mirror.